1. Field of the Invention
This invention relates to conveyer systems, and more particularly, to conveyer systems for producing translation along the longitudinal axis of a cylindrically shaped body.
2. Description of the Prior Art
Many different conveyer systems have been devised to accomplish the task of producing translation along the longitudinal axis of a cylindrically shaped body. The direction of the translation produced can either be in a horizontal plane or in a vertical plane. The more difficult task is presented when the conveyer system is required to produce translation longitudinally up and down a vertically oriented cylindrically shaped body, such as a flagpole or a tree. For systems producing vertical translation, the conveyor must not only lift its own weight, but must also lift the weight of the load which it is carrying. For these reasons, prior art conveyer systems contain very elaborate structural and mechanical arrangements to grip the cylindrical body and to provide vertical translation. Elaborate drive systems, including specially designed gears and transmissions, have been necessary to provide the required mechanical advantage so that a reasonably small engine can be used to propel the conveyer system vertically up and down.
The means of attaching prior art conveyer systems to vertically oriented, cylindrically shaped bodies has also presented substantial technical obstacles. Typically, these systems have utilized assorted combinations of metal wheels, rubber wheels, gears having a plurality of sharp teeth, tapered cylinders with sharp protruding spikes, and toothed chains. The cost of these prior art systems has been substantial since they must be designed to exert a high level of force on the periphery of the cylindrically shaped body in order to provide sufficient traction to prevent slippage in the vertical direction. This requirement dictated that a highly stressed frame member be provided which could withstand the necessary forces without itself becoming deformed.
Gear reduction systems which couple the power source to the translation-producing mechanism are typically of extremely sophisticated construction and utilize costly chains, toothed gears, worm gears or various other types of pulleys and shafts. The mechanical tolerances of the components located in the drive mechanism are critical, thereby substantially increasing the price of the conveyer system.
Virtually all relevant prior art conveyer systems also impart substantial structural damage to the pole or tree to which the conveyer is attached. Most prior art systems rely on actual mechanical penetration of the surfce of the cylindrically shaped body to prevent slippage. The use of this type of apparatus in a system where repeated up and down movements are required is unacceptable since eventually the extent of physical damage to the cylindrical body would be so substantial that it would no longer be able to support the conveyer system.
Another disadvantage of prior art conveyer systems is that they exert extremely high pressures upon the outer surface of the cylindrically shaped body. Because of this characteristic, the prior art conveyer systems can only be used with a cylindrically shaped body which is extremely strong and unyielding. Were the properties of the body otherwise, its surface would collapse due to the pressure.
A further disadvantage of prior art conveyer systems is that they can only be used with cylindrically shaped bodies having a narrow range of diameters. A conveyer system designed for use with a palm tree having a diameter of from one to two feet would not be adaptable for use with a flagpole having a three to six inch diameter.
Examples of the foregoing prior art conveyer systems are shown and described in U.S. Pat. Nos. 742,447 (Kidder), 1,299,289 (Berg), 957,473 (Olafson), 2,174,525 (Padernal), 3,520,383 (Loock), 2,654,638 (Elliott), 2,541,767 (Jones), and 2,612,724 (Llewellyn).